The invention relates to the field of laser beam deflection devices, and in particular to the use of solitons to increase figure-of-merit of laser beam deflection devices.
The most common way of achieving fast light deflection is by using micro-electro-mechanical (MEMS), acousto-optic, and electro-optic devices.
A MEMS device is essentially a tiny mirror whose direction can be changed by applying electrical stimuli to it. Due to the nature of its operation, the number of resolvable points is almost arbitrary. However, most MEMS devices used today have a response time of the order of 1 ms. Operational times of the order 1 μs have been demonstrated. There have also been proposals on how one might be able to achieve operational times perhaps as fast as 20 ns in MEMS devices that use interference rather than reflection, however, such devices have yet to be demonstrated, and what their number of resolvable points will ultimately be is not clear at this point.
Acousto-optic devices explore deflection of light by reflection from a grating, which is dynamically “written” into the material of propagation by a sound-wave. Due to the nature of their operation, the number of the resolvable points can be large, and they can be fast (up to the order 1 ns). However, the faster they are, the smaller the number of resolvable points. As one approaches the speeds of 1 ns, the number of resolvable points decreases to only a few. Furthermore, the angle of deflection is fairly sensitive to the wavelength of the light being deflected. Consequently, these devices can typically be designed to have the desired performance only within a fairly limited bandwidth.
In electro-optic devices, deflection of light is accomplished through electro-optic effect. Through the electro-optic effect, a strong electrical DC field applied to a material modifies the index of refraction of the material. If this modification is different in different parts of the material, different parts of the beam propagating through such a material can accumulate different phase-shifts. If the accumulated phase shift varies uniformly across the beam, the wave-front gets bent by an angle as shown in the example in FIG. 1.
In particular, FIG. 1 shows a panel 2 having an external DC electric field that is not applied. The beam exits the device along the same direction it entered the device. In panel 4, an external electric DC field is applied to the material. The gradient of the field is uniform and the field varies from zero (at the bottom of the material) to some maximum value (at the top of the material). Due to the electro-optic effect, the index of refraction is larger in the upper part of the material than in the lower part. Consequently, the part of the beam that travels in the upper part accumulates more phase shift than the part traveling in the lower part. As a result, the beam is deflected upwards. Note that panels 2 and 4 have a length L and width D.
Since a DC field can be turned on and off fairly rapidly, electro-optic devices can be ultra-fast; speeds of operation faster than 1 ns are not unusual. Consequently, they currently present the only feasible solution that can be used to operate at ultra-fast speeds. Unfortunately, there are some physical limitations, to be explained below, that limit the number of resolvable points of such a device to only a few.